To increase the areal storage density of a magnetic recording device, the recording layer thereof may be provided with smaller and smaller individual magnetic grains. This reduction in grain size soon reaches a “superparamagnetic limit,” at which point the magnetic grains become thermally unstable and incapable of maintaining their magnetization. The thermal stability of the magnetic grains can be increased by increasing the magnetic anisotropy thereof (e.g., by utilizing materials with higher anisotropic constants). Increasing the magnetic anisotropy of the magnetic grains, however, increases their coercivity and therefore requires a stronger magnetic field to change the magnetic orientation of the grains (e.g., in a write operation).
Energy assisted magnetic recording (EAMR) is used to address this challenge. In an EAMR system, a small spot where data is to be written is locally heated to reduce the coercivity of the magnetic grains therein for the duration of the write operation, thereby allowing materials with increased magnetic anisotropy to be used, and greater areal storage density to be exploited.
One approach to providing heat in an EAMR involves using edge-emitting lasers to direct laser light through the magnetic recording head to the magnetic media. Integrating edge-emitting lasers into a magnetic recording head, however, presents a number of technological difficulties. Vertical cavity surface emitting lasers (VCSELs) can be more easily integrated into magnetic recording heads, but a single VCSEL may not provide enough optical energy to the magnetic recording media to overcome the increased coercivity thereof, and integrating multiple VCSEL dies into a magnetic recording head would be prohibitively difficult.